Siggraph 2016: An Artist-Friendly Workflow for Panoramic HDRI

The slides and course notes files of me and my-coworker Sébastien Lachambre and Cyril Jover “An Artist-Friendly Workflow for Panoramic HDRI” are available here:

On the official PBR course website:
http://blog.selfshadow.com/publications/s2016-shading-course/

and Unity Labs website:
https://labs.unity.com/

On the asset store of Unity there is a pack of HDRI. This is a pack of 7 LatLong, 8192×4096 HDR images shot in different locations around the world. Accurate, unclamped cubemaps of interior and exterior environments; HDRIs that include the Sun are provided with an alternate version with the Sun already removed. https://www.assetstore.unity3d.com/en/#!/content/72511
Note: HDRI can be download in Unity then use in another context, they are just .exr files. There is no restriction on both commercial and non-commercial usage for them.

Few notes:
As a programmer, I was often asking myself how artists are capturing HDRI ? After few research I have noticed that very often the HDRI available on the Internet lack range or metadata information to reconstruct absolute HDRI. Worse, many HDRIs are tweaked to looks good instead of being accurate to be used as a light sources. With my co-worker we have decided to write an extensive “tutorial” that explain how to capture an accurate HDRI. We have voluntary provide a lot of details and our equipment/software recommendation list. We hope by this to save readers time when they will try to reproduce our workflow. We have consider our workflow from an artists point of view instead of a programmer point of view, trying to use commonly know artist softwares. We also limit ourselves to average budget for this kind of capture.

The course notes (~80 pages) is the interesting part of the talk, the slide are just here to give an overview. I have included a section about what I call the “path of light”. It explain what is happening inside a camera from an emit photon to its life through the optics, the sensor, then the software processing. This is not something that is needed to understand to apply our method. But it is a really interesting piece of knowledge and help to put correct words on thing :).

Lastly in the course note I have decided to integrate a section call “Look Development”. Look development is a term pretty common in VFX industry but I was surprise to see how few people know about it in the game industry. At Unity we have develop a new tools call “Look Dev” that will be experimental in the next version 5.5 beta. This is a viewer that aim to help look development with HDRIs:

Of course, this kind of tools already exist, Substance, Marmoset, Mari, etc… The benefit of having one integrated into Unity is that it is WYSIWYG (What you see is what you get) in your Unity game.

Finally I have chose to add some digression about how to remove the sun and replace it with analytic directional light of similar intensity as it is often either not discuss or resume to a single sentence in others documents. This is currently a complex topics and I will be happy to see more technical discussion around this topics.

We hope that our document will help people to take their first steps into accurate HDRI capture and see more absolute HDRI appearing. The document come with some materials: Various Photoshop Actions that we use and set of HDRIs. One is available on publications website but we expect to deliver soon a package of HDRI via the Unity Asset Store for free that include all versions (white balance, absolute, unprocessed…) of an HDRI and metadata.  At first we were willing to distribute all the CR2 too but the size of the download become crazy insane and we think to do it only for one HDRI, so programmer willing to do some test will be able to do it.

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